High-pressure pump

ABSTRACT

A high pressure pump for preventing distortion of a sealing surface or a cylinder form. The high pressure pump has an intermediate member including a cylinder body ( 4 ) having a pressurizing chamber ( 14 ) communicated with a cylinder ( 4   a ) accommodating a plunger ( 12 ). Fluid in the pressurizing chamber is pressurized by reciprocating the plunger. The intermediate member is arranged between a cover ( 6 ) and a flange ( 8 ) and is clamped by clamping bolts ( 40 ). An electromagnetic spill valve ( 10 ) for receiving reaction force from the pressurizing chamber when the fluid in the pressurizing chamber is pressurized is attached to the cover ( 6 ) at a position for reducing the clamping force applied to the intermediate member by the clamping bolts.

TECHNICAL FIELD

[0001] The present invention relates to a high pressure pump, and moreparticularly, to a high pressure pump having an intermediate member,which includes a cylinder body to pressurize fluid in a pressurizingchamber by reciprocating a plunger in a cylinder and which is arrangedbetween two clamping members, the intermediate member being clamped by aclamping bolt, which extends between the two clamping members, by meansof the clamping members.

BACKGROUND ART

[0002] For example, Japanese Laid-Open Patent Publication No. 11-210598discloses a high pressure fuel pump used for an engine such as acylinder injection type gasoline engine. In the high pressure fuel pump,to improve the machining characteristics and assembling characteristics,an intermediate member such as a sleeve (corresponding to cylinder body)is clamped between members such as a bracket along the axial directionand fastened to a casing by a clamping bolt.

[0003] Further, in the high pressure fuel pump, if the sleeve is justclamped, its cylinder form tends to be easily deformed. Therefore, aslit is formed between a clamping portion of the sleeve and thecylinder. The slit prevents the deformation caused by clampingcylindrical clamping members from affecting the cylinder form.

[0004] However, the clamping bolt for clamping the sleeve requires arelatively large initial, axial force. This is because the initial,axial force includes not only the axial force required for sealing theintermediate member but also requires the axial force required forcoping with changes in the axial force resulting from fuel pressurepulsation that is produced when the high pressure pump is activated.Therefore, taking into consideration the change in the axial force ofthe high pressure pump, the intermediate member must be clamped with arelatively large initial, axial force when manufactured. However, whenthe intermediate member is clamped by a large initial, axial force withthe clamping bolt, deformation of a sealing surface of the intermediatemember or deformation of the cylinder form occurs. It is difficult toprevent such distortion.

DISCLOSURE OF THE INVENTION

[0005] It is an object of the present invention to provide a highpressure pump and a coupling structure of a high pressure pump havingsmall initial axial force of a clamping bolt and being capable ofpreventing distortion of a sealing surface or a cylinder form.

[0006] One aspect of the present invention provides a high pressure pumphaving an intermediate member including a cylinder body having apressurizing chamber communicated with a cylinder accommodating aplunger. Fluid in the pressurizing chamber is pressurized byreciprocating the plunger. The high pressure pump includes two clampingmembers arranged on two sides of the intermediate member, a clampingbolt extending between the two clamping members to clamp theintermediate member with the two clamping members, and a member forreceiving reaction force from the pressurizing chamber when the fluid inthe pressurizing chamber is pressurized. The member for receiving thereaction force is attached to one of the two clamping members at aposition for reducing the clamping force applied to the intermediatemember by the clamping bolt.

[0007] In this structure, the member for receiving the reaction force isattached so that the reaction force of the pressurizing chamber isapplied to the clamping member to reduce the clamping force applied tothe intermediate member. Therefore, even if the reaction force of thepressurizing chamber, which is produced by fluid pressure pulsationduring operation of the high pressure pump, is applied to the clampingmember, the member for receiving the reaction force decreases thereaction force produced by the clamping of the intermediate member.Accordingly, the total reaction force becomes smaller than a sum of thereaction force of the pressurizing chamber and the reaction forceproduced when by clamping the intermediate member. The change of axialforce caused by the fluid pressure pulsation during operation of thehigh pressure pump decreases. As a result, the initial axial force isdecreased, and distortion of a sealing surface or a cylinder form isprevented.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] The invention, together with objects and advantages thereof, maybest be understood by reference to the following description of thepresently preferred embodiments together with the accompanying drawingsin which:

[0009]FIG. 1(A) is a schematic diagram of a high pressure pump accordingto the present invention in a stationary state, and FIG. 1(B) is aschematic diagram of a prior art high pressure pump in an stationarystate.

[0010]FIG. 2(A) is a schematic diagram of a high pressure pump accordingto the present invention in a dynamic state, and FIG. 2(B) is aschematic diagram of a prior art high pressure fuel pump in a dynamicstate.

[0011]FIG. 3 is a cross sectional view of a high pressure pump accordingto an embodiment of the present invention.

[0012]FIG. 4 is a schematic diagram of a fuel supplying system for aninternal combustion engine incorporating the high pressure fuel pump.

[0013]FIG. 5 is a cross sectional view of a high pressure pump accordingto an embodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

[0014] Before describing a high pressure pump according to an embodimentof the present invention, the principle of the present invention will bediscussed. In the high pressure pump of the present invention, which isschematically shown in FIG. 1(A), an intermediate member M including acylinder body is arranged between two clamping members E1, E2. Theintermediate member M is clamped between the clamping members E1, E2 byclamping bolts B1, B2, which extend between the clamping members E1, E2.A member G is attached the clamping member E1 on the side that isopposite to the side where the intermediate member M is clamped. Whenfluid in a pressurizing chamber I is compressed by a plunger D andpressurized, the member G receives reaction force from the pressurizingchamber I.

[0015] In the high pressure pump of FIG. 1(A), when the intermediatemember M is clamped by the clamping bolts B1, B2, the intermediatemember M is elastically deformed and reaction force F0 is generated. Therelationship between the reaction force F0 and the axial force Bfproduced by the clamping bolts B1, B2 is represented by the followingequation [1].

F0=2·Bf  [1]

[0016] In a prior art high pressure pump, which is shown in FIG. 1(B),when fluid is compressed and pressurized in a pressurizing chamber I bya plunger d, a member g receives reaction force from the pressurizingchamber i. The member g and intermediate members m1, m2 are arrangedbetween two clamping members e1, e2. In this case, when the intermediatemembers m1, m2 and the member g are clamped by the clamping bolts b1,b2, the intermediate members m1, m2 and the member g are elasticallydeformed and the reaction force F0 is generated. The relationshipbetween the clamping bolts b1, b2 and the axial force bf is representedby the following equation [2].

F0=2·bf  [2]

[0017] Accordingly, the relationship between the reaction force f0 andthe axial force is the same in equations [1] and [2]. Therefore, intightening when the high pressure pump stops, the axial force Bf of theclamping bolts B1, B2 of FIG. 1(A) is set same as the axial force bf ofthe clamping bolts b1, b2 of FIG. 1(B).

[0018] However, when reaction force FN is generated as the pressurizingchamber I is pressurized, the member G receives the reaction force FNfrom the pressurizing chamber I in the high pressure pump of the presentinvention shown in FIG. 2(A). Because the member G is arranged on theside opposite to the clamping side of the intermediate member M, thereaction force FN acts as a lifting force FU applied to the clampingmember E1. The lifting force FU is an element of the axial force Bfgenerated at the clamping bolts B1, B2. Another element of the axialforce Bf is reaction force FM from the intermediate member M. Therefore,the axial force Bf is represented by the following equation [3].

2·Bf=FU+FM  [3]

[0019] The reaction force FM from the intermediate member M decreasesthe clamping force applied to the intermediate member M in accordancewith the amount the clamping member E1 is lifted by the lifting forceFU. This decreases the compression amount of the intermediate member M.Thus, the reaction force FM is smaller than the reaction force F0 ofFIG. 1(A).

[0020] On the other hand, in the high pressure pump of the prior artshown in FIG. 2(B), the member g that receives the reaction force FNfrom the pressurizing chamber I is arranged on the clamping side withthe intermediate members m1, m2. In this case, the generated liftingforce FU of the clamping member e1 resulting from the reaction force FNis an element of the axial force bf generated at the clamping bolts b1,b2. Another element of the axial force bf is the reaction force Fm fromthe intermediate members m1, m2 and the element g. Therefore, the axialforce bf is represented by the following equation [4].

2·bf=FU+Fm  [4]

[0021] The member g is arranged together with the intermediate member mlbetween the clamping member e1 and the pressurizing chamber i. Thiscauses the reaction force FN to increase the compression amount of themember g and the intermediate member m1. Therefore, the reaction forceis almost same as the reaction force F0 in FIG. 1(B). Even if thereaction force FN decreases, the decreased degree is less than thedifference between the reaction force F0 in FIG. 1(A) and the reactionforce FM in FIG. 2(A). That is, FM<Fm. Therefore, in the state of FIGS.2(A) and 2(B), Bf<bf is satisfied. As a result, in the high pressurepump of the present invention, when fluid in the pressurizing chamber ispressurized, an increase in the axial force of the clamping bolt isincreased by the reaction force received from the pressurizing chamber.In other words, change in the axial force caused by fluid pressurepulsation during operation of the high pressure pump decreases. Thisenables the initial axial force of the clamping bolt to be relativelysmall. Therefore, the sealing surface and the cylinder form areprevented from being distorted.

[0022]FIG. 3 is a cross sectional view of a high pressure fuel pump 2according to one embodiment of the present invention. The high pressurefuel pump 2 is incorporated in a cylinder injection type gasoline engineE, as shown in FIG. 4, and generates high pressure fuel injected intocombustion chambers of the engine E.

[0023] As shown in FIG. 3, the high pressure fuel pump 2 has a cylinderbody 4, a cover 6, a flange 8 and an electromagnetic spill valve 10. Acylinder 4 a is formed along the axis of the cylinder body 4. A plunger12 is supported in the cylinder 4 a slidably in the axial direction. Apressurizing chamber 14, which is communicated with the cylinder 4 a, isdefined at the distal side of the cylinder 4 a in the cylinder body 4. Avolume of the pressurizing chamber 14 is varied as the plunger 12 movesinto or out of the pressurizing chamber 14.

[0024] The pressurizing chamber 14 is connected to a check valve 18 viaa fuel pressure supply passage 16. The check valve 18 is connected to afuel distribution pipe 20 (FIG. 4). The check valve 18 is opened whenthe fuel in the pressurizing chamber 14 is pressurized and the highpressure fuel is supplied to the fuel distribution pipe 20.

[0025] A spring seat 22 and a lifter guide 24 are stacked upon eachother at the lower side of the cylinder body 4. An oil seal 26 isattached to the inner surface of the spring seat 22. The oil seal 26 isgenerally cylindrical and has a lower portion 26 a that slidablycontacts the peripheral surface of the plunger 12. Fuel leaked from aspace between the plunger 12 and the cylinder 4 a is stored in a fuelstoring chamber 26 b of the oil seal 26 and returned to a fuel tank Tvia a fuel discharge passage (not shown), which is connected to the fuelstoring chamber 26 b.

[0026] A lifter 28 is accommodated in the lifter guide 24 slidably inthe axial direction. A projected seat 28 b is formed on an inner surfaceof a bottom plate 28 a of the lifter 28. A lower end portion 12 a of theplunger 12 engages the projected seat 28 b. The lower end portion 12 aof the plunger 12 is engaged with a retainer 30. A spring 32 is arrangedbetween the spring seat 22 and the retainer 30 in a compressed state.The lower end portion 12 a of the plunger 12 is pressed toward theprojected seat 28 b of the lifter 28 by the spring 32. The pressingforce from the lower end portion 12 a of the plunger 12 causes thebottom plate 28 a of the lifter 28 to engage a fuel pump cam 34.

[0027] When the fuel pump cam 34 is rotated in cooperation with therotation of the engine E, a cam nose of the fuel pump cam 34 pushes thebottom plate 28 a upward and lifts the lifter 28. In cooperation withthe lifter 28, the plunger 12 moves upward and narrows the pressurizingchamber 14. This lifting stroke corresponds to a fuel pressurizing stokeperformed in the pressurizing chamber 14.

[0028] The electromagnetic spill valve 10 facing the pressurizingchamber 14 is closed at a proper timing during the pressurizing stroke.In the pressurizing process, prior to the closing of the electromagneticspill valve 10, the fuel in the pressurizing chamber 14 returns to thelow pressure side fuel tank T via a space between a seat 10 b and apoppet valve 10 a of the electromagnetic spill valve 10, a fuel passage10 c, a gallery 10 d, and a low pressure fuel passage 35. Therefore,fuel is not supplied from the pressurizing chamber 14 to the fueldistribution pipe 20. When an electromagnetic circuit in theelectromagnetic spill valve 10 causes the poppet valve 10 a to come intocontact with a seat 19 b, the low pressure side fuel tank T and thepressurizing chamber 14 are disconnected (the state of FIG. 4). As aresult, the pressure of the fuel in the pressurizing chamber 14increases suddenly and generates high pressure fuel. This opens thecheck valve 18 with the high pressure fuel and supplies the highpressure fuel to the distribution pipe 20.

[0029] When the cam nose of the fuel pump cam 34 starts to movedownward, the urging force of the spring 32 starts to gradually move thelifter 28 and the plunger 12 downward (intake stroke). When the intakestroke starts, the electromagnetic circuit in the electromagnetic spillvalve 10 separates the poppet valve 10 a from the seat 10 b and opensthe electromagnetic spill valve 10. This draws fuel into thepressurizing chamber 14 from the low pressure fuel passage 35 throughthe gallery 10 d, the fuel passage 10 c, and the space between thepoppet valve 10 a and the seat 10 b (the state of FIG. 3).

[0030] The pressurizing stroke and the suction stroke are performedrepeatedly. The closing timing of the electromagnetic spill valve 10during the pressurizing stroke is feedback controlled to adjust the fuelpressure in the fuel distribution pipe 20 at the optimal pressure forinjecting fuel from the fuel injection valve 38. The feedback control isexecuted by an electric control unit (ECU) 36 in accordance with thefuel pressure in the fuel distribution pipe 20, which is detected by afuel pressure sensor 20 a, and the running condition of the engine.

[0031] The cylinder body 4, the spring seat 22, and the lifter guide 24form an intermediate member of the high pressure fuel pump 2 and arearranged between the cover 6 (first clamping member) and the flange 8(second clamping member) in a stacked state. The electromagnetic spillvalve 10 has a base plate 10 f, and the base plate 10 f is attached tothe cover 6 by attaching bolts 10 e at a side opposite to the side wherethe cylinder body 4, the spring seat 22, and the lifter guide 24 areclamped.

[0032] The cylinder body 4, the spring seat 22, and the lifter guide 24are clamped between the cover 6 and the flange 8 by clamping bolts 40that extends between the cover 6 and the flange 8. In the crosssectional view of FIG. 3, the cross section at the right side of theaxis of the high pressure fuel pump 2 differs from the cross section atthe left side of the axis. That is, the left cross sectional half andthe right cross sectional half are views taken at different cuttingangles. Therefore, only one of a plurality of clamping bolts 40 is shownin FIG. 3. FIG. 5 shows a cross sectional view of the high pressure fuelpump 2 taken along the same cutting plane. As shown in FIG. 5, twoclamping bolts 40 are arranged about the axis in a symmetric manner. Inthis embodiment, two sets of clamping bolts 40 are arranged in asymmetric manner around the cylinder body 4, the spring seat 22, and thelifter guide 24 to couple the cover 6 and the flange 8 to each other.

[0033] In the same manner, the attaching bolts 10 e for fastening theelectromagnetic spill valve 10 to the cover 6 are symmetrically arrangedabout the axis of the cylinder 12. In this embodiment, the base plate 10f of the electromagnetic spill valve 10 is attached to the cover 6 bytwo sets of the attaching bolts 10 e.

[0034] The entire high pressure fuel pump 2 is fixed to a cylinder headcover 52, which serves as a supporting body, by a fastening bolt 54. Theflange 8 has clamping bolt holes 8 b, through which the clamping bolts40 extend, and fastening bolt holes 8 c, through which the fasteningbolt 54 extend. The fastening bolt holes 8 c are located closer to theperipheral portion than the clamping bolt holes 8 b. The fastening bolts54 are inserted in the fastening bolt holes 8 c in a direction oppositeto the direction of the clamping bolts 40 and screwed into screwapertures 52 a formed in the cylinder head cover 52. In this embodiment,two sets of fastening bolts 54 are arranged symmetrically about the axisof the cylinder 12. In this manner, the high pressure fuel pump 2 isprovided in the cylinder head cover 52. The bottom plate 28 a of thelifter 28 is exposed from a through hole 53 of the cylinder head cover52 and is engaged with the fuel pump cam 34 of the engine E. In thismanner, the plunger 12 reciprocates in the cylinder 4 a in cooperationwith the rotation of the engine E.

[0035] The high pressure fuel pump 2 of the present invention has thefollowing advantages.

[0036] (1) In the high pressure fuel pump 2, the cylinder body 4, thespring seat 22, and the lifter guide 24 are arranged between the cover 6and the flange 8. The cylinder body 4, the spring seat 22 and the lifterguide 24 are clamped by the clamping bolts 40, which extend between thecover 6 and the flange 8.

[0037] The electromagnetic spill valve 10 is attached to the cover 6 onthe side that is opposite to the side where the cylinder body 4, thespring seat 22 and the lifter guide 24 are clamped. The poppet valve 10a of the electromagnetic spill valve 10 receives the reaction force (thearrow of FIG. 3) from the pressurizing chamber 14 when coming intocontact with the seat 10 b. Therefore, as shown in FIGS. 1(A) and 2(A),an increase in the axial force of the clamping bolts 40, which resultsfrom the reaction force received by the electromagnetic spill valve 10from the pressurizing chamber 14, is small in comparison to when theelectromagnetic spill valve 10 is arranged on the same side as thecylinder body 4, the spring seat 22, and the lifter guide 24.

[0038] When the base plate 10 f of the electromagnetic spill valve 10receives the reaction force from the pressurizing chamber 14, the baseplate 10 f lifts the attaching bolts 10 e. This lifts the cover 6 andreduces the clamping force applied to the cylinder body 4, the springseat 22, and the lifter guide 24 is loosened. This decreases thereaction force that results from the clamping of the cylinder body 4,the spring seat 22, and the lifter guide 24. In this manner, even if thereaction force of the pressurizing chamber 14 is applied to the cover 6by the fuel pressure pulsation produced during operation of the highpressure fuel pump 2, the reaction force resulting from the tighteningof the cylinder body 4, the spring seat 22 and the lifter guide 24decreases. Therefore, the total reaction force is smaller than the sumof the two reaction forces.

[0039] Accordingly, the axial force change caused by the fuel pressurepulsation when the high pressure fuel pump 2 is operated decreases. As aresult, the initial axial force of the clamping bolts 40 decreases, anddistortion of each sealing surface of the cover 6, the cylinder body 4,the spring seat 22, the lifter guide 24 and the flange 8 and distortionof the form of the cylinder 4 a are prevented. This improves thedurability of the high pressure fuel pump 2.

[0040] (2) The reaction force of the pressurizing chamber 14 applied tothe attaching bolts 10 e via the base plate 10 f of the electromagneticspill valve 10 acts in a direction for lifting the attaching bolts 10 e.Therefore, the reaction force resulting from the elastic deformation ofthe base plate 10 f near the attaching bolts 10 e decreased as the fuelpressure increases. The initial axial force of the attaching bolts 10 ealso decreases, and distortion of the sealing surface of theelectromagnetic spill valve 10 and the cover 6 is prevented.

[0041] Therefore, the present examples and embodiments are to beconsidered as illustrative and not restrictive and the invention is notto be limited to the details given herein, but may be modified withinthe scope and equivalence of the appended claims. The high pressure fuelpump of the present invention may be installed to a cylinder head of anengine.

1. A high pressure pump characterized by: a plunger (12); anintermediate member (4, 22, 24) having a cylinder (4 a) foraccommodating the plunger and a pressurizing chamber (14) communicatedwith the cylinder and including a cylinder body (4) for pressurizingfluid in the pressurizing chamber by reciprocating the plunger; twoclamping members (6, 8) arranged on two sides of the intermediatemember; a clamping bolt (40) extending between the two clamping membersto clamp the intermediate member with the two clamping members; and amember (10) for receiving reaction force from the pressurizing chamberwhen the fluid in the pressurizing chamber is pressurized, wherein themember for receiving the reaction force is attached to one of the twoclamping members at a position for reducing the clamping force appliedto the intermediate member by the clamping bolt.
 2. The high pressurepump according to claim 1, characterized in that the member forreceiving the reaction force is attached to one of the two clampingmembers at a side opposite to the side at which the intermediate memberis clamped by the clamping bolt.
 3. The high pressure pump according toclaim 2, characterized in that the member for receiving the reactionforce is arranged facing the pressurizing chamber and functions as anelectromagnetic valve (10) for pressurizing the fluid in thepressurizing chamber by stopping movement of the fluid from thepressurizing chamber to a low pressure area (T).
 4. The high pressurepump according to claim 2 or 3, characterized in that the fluid is fuelused for a cylinder injection type internal combustion engine.
 5. Thehigh pressure pump according to claim 4, characterized in that theclamping member (8) differing from the clamping member (6) to which themember for receiving the reaction force is attached is attached to acylinder head cover (52) of the internal combustion engine.
 6. The highpressure pump according to claim 4 or 5, characterized in that theplunger is driven by a fuel pump cam (34) rotated in cooperation withrotation of the internal combustion engine and reciprocates in thecylinder.
 7. The high pressure pump according to one of claims 1 to 6,characterized in that the member for receiving the reaction forceincludes a base plate (10 f), and the high pressure pump furtherincluding an attaching bolt (10 e) for fastening the base plate to oneof the two clamping members.
 8. The high pressure pump according toclaim 7, characterized in that the reaction force from the pressurizingchamber acts in a direction for lifting the attaching bolt by means ofthe base plate.